1. Field of the Invention
The invention relates to a circuit breaker apparatus, more especially a multiphase circuit breaker comprising a common quick trip mechanism which may be set and tripped by means of a local manual control member, a multiplicity of power circuits each comprising between two terminals a switch which is placed in an arc extinction chamber and whose mobile contact is connected to said mechanism so as to be closed or opened thereby, detectors which react to over currents of different kinds in these circuits by causing said mechanism to trip and, consequently, the automatic opening of the switches, and an electromagnet which is associated with the apparatus for causing remote controlled opening of the mobile contacts of the switches not involving the tripping of said mechanism.
2. Description of the Prior Art
Such apparatus are used in electric installations where it is desired both to protect the lines as well as the loads which are associated therewith, and to further have the faculty of interrupting the supply of these loads by means of a remote control, and by a channel separate from the one which comprises contactors usually placed between the apparatus and a corresponding load; it is also possible to interrupt the supply of a group of machines fed by this apparatus, without for all that being forced to de-energize the corresponding contactors and so to cause the combination of their states to disappear, which then allows an immediate start up to be effected under the same conditions.
An apparatus is already known, for example from the patent application PCT No. WO 83/02680, whose general construction is to be found in the one mentioned above, for answering the needs of users when the nominal currents which flow therethrough are less than a hundred amperes or so.
When the nominal currents exceed this level and when consequently the mass of the contact pieces as well as the presumed currents of the short circuits increase correspondingly, the limitation devices using coils placed in series in the circuit for attracting a plunger core which strikes the mobile contact, become inefficient.
Recourse is then had to apparatus in which considerable energy is accumulated in powerful springs of a quick trip mechanism, which is set for example by means of a local control member and which is then released by the action of the over current detectors placed in series when high over currents appear.
When such over currents reach the thresholds of the excessive currents observed when outright short circuits occur, it is moreover necessary to limit their peak by providing a very rapid opening of the switch which therefore only calls into play the smallest possible masses and which essentially uses the electro-dynamic repulsion forces which are communicated without any delay to the conductors when these latter have a particular geometry; the effect of these forces may be improved in a way known per se by the cooperation of magnetizable masses placed in the vicinity.
In the known apparatus which has just been mentioned, small sized torsion springs apply their nominal torque without any multiplication to a piece carrying the mobile contact, so as to confirm mechanically, and so with a certain delay, the open position which the mobile contact takes with a certain delay; this is itself imputable on the one hand to the dynamic response time which acts on the movement of a magnetic striker and, on the other hand, to the very nature of the magnetic phenomena which govern its attraction; these phenomena which are more especially due to saturation confer then a limit on the efficiency of the currents, whereas that of the electrodynamic repulsion phenomena increases substantially as the square root of these currents, all other things being equal.
In addition, in this known apparatus, the manual opening and closing effected by the local control member are operated at slow speed because the torsion springs whose presence was mentioned above only come into play during the automatic opening procedure; this drawback which appears because of the use of a direct kinematic connection between the local manual control member becomes a defect when the nominal currents exceed a certain value.
To these disadvantages, which only appear with the increase of the nominal current, must be added those which result from a permanent connection of the armature of the electromagnet not only with the support of the mobile contact of the switch but also with the operating member; such an arrangement which causes a more rapid wear of the parts of the mechanism and in fact forces the operator to exert a greater force on the manual control member, has the drawback that remote operated closure of the switch cannot be prevented by the operator unless he permanently maintains his action on said control member.
Moreover if, with such a permanent connection, it is necessary either to actuate switches whose nominal current is high by means of a force accumulating mechanism or to simultaneously set this mechanism by a channel parallel to that which should actuate the switches, it would be necessary to give this electromagnet dimensions larger than those which are strictly indispensable for separating a mobile contact from a fixed contact; apart from the exaggerated character of the dimensions which this electromagnet might require, it will be noted that the trend of the attraction curve of an electromagnet is not compatible with the curve of the resistant forces presented by the travel of a small volume force accumulating mechanism, in which the initial forces to be provided are much greater than those which exist at the end of this travel.